Read only memory (ROM) structures have been successfully employed as nonvolatile semiconductor memory devices. Most ROM designs and process usually can be described by three elements. First, buried bit lines are placed in a silicon substrate. The bit lines usually are heavily doped regions, opposite in conductive type with the substrate. Next word lines, usually polysilicon, are placed on gate oxide layers, perpendicular to buried bit lines. Finally, a specific channel region, arising from the intersection of the bit and word lines, is selectively programmed to electrically respond differently then intersections that have not received the programmed treatment. The programmable cell, as it electrically respond differently then intersections that have not received the programmed treatment. The programmable cell, as it is normally referred to , can be created either prior to, or after the fabrication of the polysilicon word line. The programmable cell can be achieved via many techniques. Most ROM designs and process are (1) buried line structure as seen in the reference "G. Hong, U.S. Pat. No.: 5,635,415 (1997)" and (2) ion implantation resulting in a different threshold voltage as in the reference "Y. J. Wann, et al., U.S. Pat. No.: 5,514,610 (1996)", etc. For the second case, an additional mask is necessary to achieve different threshold voltage.